This invention relates to a control or fixed station which is for use in a radio telephone network system to carry out communication between the control station and a plurality of movable radio telephone sets, such as cordless telephone sets or mobile telephone sets.
A conventional radio telephone network system of the type described comprises a control station which is connected to a private branch exchange (abbreviated to a PBX) or another exchange. The control station serves to communicate within a preassigned service zone through radio channels with a plurality of radio telephone sets, each of which is movable over the service area. The radio channels are divided into a control channel for control operation and a plurality of speech channels for transmission of speech signals.
More particularly, the control station comprises a radio connecting equipment section or group (CEG) for selectively coupling the radio telephone sets through the radio channels and a radio control unit (RCU) between the exchange and the radio connecting section.
A proposal has recently been made about arranging or locating a plurality of connecting equipment units (CE) as the radio connecting section in a common service zone. In this event, a preselected one of the connecting equipment units is operable in the service zone as a control equipment unit for monitoring the control channel to process an originating call and a terminating call and to indicate the speech channels while the other connecting equipment units are operable as speech equipment units for forming speech paths through the indicated speech channels. Thus, the control equipment unit and the speech equipment units are determined in the service zone without being spatially and temporally changed. At any rate, such an arrangement of the connecting equipment units enables communication of each radio telephone set through any one of the connecting equipment units no matter where each radio telephone set is present in the service zone.
However, a plurality of the connecting equipment units should be arranged in the service zone even when traffic is not very heavy. This means that superfluous facilities must be installed in the control station. Therefore, the control station inevitably becomes expensive.
On the other hand, consideration might be made about controlling each connecting equipment unit in a time division fashion to monitor the control channel and to switch the control channel to a selected one of the speech channels. Such monitoring and switching operations of each connecting equipment unit may dispense with superfluous facilities in the control station.
However, it often happens that none of the connecting equipment units transiently monitor the control channel in the control station in question, with all the connecting equipment units switched to the speech channels. Under the circumstances, a call might take place from the exchange or at least one of the radio telephone sets while none of the connecting equipment units monitor the control channel. This results in prolongation of a response to the call in the control station because each connecting equipment unit can not quickly respond to the call.